1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more specifically, relates to a method of fabricating a semiconductor device which is capable of forming linear patterns on a substrate.
2. Description of the Related Art
With the continuous development of semiconductor techniques as well as the increasing shrinkage of critical dimensions, a hard mask technology taking, for example, a titanium nitride TiN as a representation, has become a mainstream in back-end-of-line (BEOL) fabrication. In the hard mask technology, in order to form a patterned hard mask on a substrate, the following processing as shown in FIGS. 1A-1E are usually adopted:    (1) depositing a TiN layer 102 on a substrate 101;    (2) depositing a bottom anti-reflective coating (Barc) (not shown) on the TiN layer;    (3) coating a photo-resist layer on the Barc;    (4) performing exposure and development for the photo-resist layer, forming a patterned photo-resist layer 103, thereby exposing a portion of the Barc, as shown in FIG. 1A;    (5) conducting a reactive ion etching on the exposed Barc using a mixed gas of Cl2 and O2, to remove this portion of the Barc, thereby exposing the underlying TiN;    (6) conducting a reactive ion etching on the exposed TiN using a mixed gas of CH4 and Cl2, to remove this portion of TiN;    (7) removing the photo-resist on the substrate, thereby forming a patterned TiN layer 104 on the substrate, as shown in FIG. 1B.
Next, on the basis of the patterned hard mask, steps of coating a photo-resist layer, performing exposure and development and forming a patterned photo-resist layer 105 are performed once again, as shown in FIG. 1C.
Next, a desired trench is formed on the substrate by a two-step etch.
The first-step etch takes the patterned photo-resist shown in FIG. 1C as a mask to conduct an etch on the substrate, thus forming a via 106. The photo-resist layer is then removed (as shown in FIG. 1D). And next, the substrate is etched continuously by taking the patterned hard mask as a mask, and finally a desired trench 107 is formed on the substrate (as shown in FIG. 1E).
Meanwhile, because of the shrinkage of critical dimensions, the influence of the line width roughness (LWR) of the photo-resist layer on the time dependent dielectric breakdown (TDDB) related performance becomes greater and greater.
As shown in FIG. 2, the line width roughness of the photo-resist includes a low-frequency line width roughness (L-LWR) 202 and a high-frequency line width roughness (H-LWR) 201. In the prior art, a method is proposed in which the patterned photo-resist is pre-treated through CHF3 before etching, so as to improve the high-frequency line width roughness of the photo-resist. Engelmann has also proposed a method of conducting a plasma treatment on the photo-resist surface with C4F8/Ar (Engelmann. S “Plasma-surface interactions of advanced photo-resists with C4F8/Ar discharges”, Journal of Vac Science & Technology B: 2009).
However, since fluorine-based gases may cause corrosion to hard masks such as titanium nitride, these treatment methods are not applicable in fabrications having hard masks.
Thus, there is a need for a new technology to address any problems mentioned above in the prior art.